Peter-John Meynell of ICEM presented on the work done on biomonitoring of macroinvertebrates on the Nam Ou river in Laos as part of an IFC funded project.

1. MACRO-INVERTEBRATE SAMPLING
ON THE NAM OU RIVER
Peter-John Meynell
WLE Forum
10 November 2016
November 11, 2016

2. MACRO-INVERTEBRATE SAMPLING ON THE NAM OU RIVER
Carried out during field work for
developing the Nam Ou River Basin Profile
January/February 2016
Eight case study villages to develop mini-
profiles of the river and its use
• Two villages per zone
• One on mainstream and one on a
tributary
November 11, 2016
Ban Nagnao
Ban
Phoumuang
/Homsang
Ban Pakban
Ban Sopnao
Ban
Buamsom
Ban
Sopkhong
Ban Pak
Nga
Ban Pak Ou

3. Sampling with nets along banks and shallow
gravel/rock boTom
Using simple Southern African Scoring System
IdenUfy macroinvertebrates according to
group, not species
10 sites sampled, but some sites could not be
sampled because of high or fluctuaUng water
levels

4. QUICK KEY TO IDENTIFY MACRO-INVERTEBRATE GROUPS

5. SCORE SHEET TO RECORD PRESENCE OF GROUPS

6. MACRO-INVERTEBRATE SAMPLING RESULTS
Date Description
Flat w
orm
s
W
orm
s
Leeches
Crabs and shrim
ps
StonefliesM
innow
m
ayflies
Other m
ayflies
Dam
selfliesDragon fliesBugs and Beetles
Caddis fliesTrue flies, Diptera
M
olluscs
M
egalopteraTadpoles
Fish
Total scoreAverage
Score 3 2 2 6 17 5 11 4 6 5 9 2 4 9
01-Feb Nam Ou source 17 11 6 5 9 2 x x 50 8.3
02-Feb Natural site between Source and Gnot Ou town 6 17 11 6 5 9 4 9 67 8.3
02-Feb Bridge below Gnot Ou town 17 5 11 6 5 4 x 48 8.0
03-Feb Ban Phoumouang boat landing Biosurvey not done because river is now part of reservoir
05-Feb Pakban Biosurvey not done because at time of sampling the water level had risen by 1 m between am and pm
08-Feb Ban Sopkong FCZ DO profile 6 11 6 5 9 4 x x 41 6.8
30-Jan Ban PakNga 6 11 5 4 x 26 6.5
08-Jan Ban Hatkhe 6 5 9 4 x 24 6.0
29-Jan Island near Ban Vangle 6 11 5 4 x 26 6.5
Tributaries
31-Jan Nam Kor - fast water 6 5 11 6 5 9 2 4 x 48 6.0
slow water 6 5 11 5 4 9 x 40 6.2
31-Jan Confluence of Nam Kor and Nam Phak 6 5 11 6 5 9 2 4 48 6.0
06-Feb Ban SopNao 5 11 6 5 9 36 7.2
Colour code for rocky type rivers
Unmodified (Natural condition) >7.9
Largely natural/few modifications (Good condition) 6.8 - 7.9
Moderatley modified (Fair condition) 6.1-6.8
Largely modified (Poor condition) 5.1-6.1
Seriously/critically modified (Very Poor condition) <5.1

7. NATURAL CONDITION, LARGELY UNMODIFIED

8. GNOD OU BRIDGE SAMPLING SITE
Natural conditions according to
macroinvertbrates, but river weed
growth showing signs of eutrophication

9. RIVER HABITAT SURVEY
• Study Google Earth images and topographic maps of the area
• Use river habitat survey observaUon on:
• River features – width, flow rate, rapids, riffles, pools, narrows, channels,
midstream rocks, sandbars, in channel bushes and shrubs, tributary joining
• Presence and character of islands – small, medium sized, large,
vegetated or cultivated, with houses
• River bed – rocks and boulders, pebbles, gravel, sand, mud
• River bank - rocks and boulders, pebbles, gravel, sand, mud, man-made,
structures
• Aquatic vegetation – submerged water weed, floating plants, emergent
plants, bushes and shrubs in the river, trees growing in the river
• River bank vegetation – reeds and grasses, bushes and shrubs, large
trees
• People using the river – fishers, river bank gardeners, NTFP harvesters,
small scale gold panners

10. PAK OU ROAD BRIDGE – DEEP POOL (20 M)

11. BUILDING RIVER HABITAT
MAPS – UPSTREAM FROM PAK
OU

12. CHALLENGES AND CONSTRAINTS
1. Macro-invertebrate sampling appeared to be effecUve in showing river health
especially when used with other observaUons e.g. water quality and habitat
surveys
2. Easier to carry out in smaller, shallower rivers
3. Larger rivers are oeen deep and fast flowing, with steep banks – safety issue
4. Important to select the best habitats to sample
• Gravel and rocky river beds with shallow, gently sloping banks are best
• Slower moving reaches with water weeds
• Sand bars tend to be rather poor substrates
5. Recent and rapid changes (increase and decrease) in water level tends to
depress macro-invertebrate populaUons, e.g. from recent rain storms,
beginning of wet season, and flow changes from hydropower.